Precision distributed parameter delay line

ABSTRACT

A precision distributed parameter delay line for use in high speed circuitry requiring very precise nanosecond delay intervals. The delay line, in one preferred embodiment, comprises a section of coaxial cable transmission line having a central conductor and a coaxially aligned conductive sheath with the sheath preferably being insulated over its length. The section of coaxial cable tranmission line functions as a low impedance delay element of extremely small outer diameter whose length may be adjusted to provide delays of from tenths to hundreds of nanoseconds. The nature and size of the delay line is such as to make it extremely adaptable to being coiled so as to significantly reduce the amount of space which it occupies. A very short section of coaxial cable transmission line of similar design and impedance characteristics is coupled to the input and/or output ends of the coaxial cable transmission line section central conductor to improve the rise time and provide an extremely high delay to rise time ratio, low insertion loss, low characteristic impedance and is adaptable for use over a wide frequency bandwidth. The delay line may also take the form of a printed circuit of the microstrip type transmission line comprised of an elongated, preferably undulating conductive strip separated from a conductive ground plane by a suitable dielectric with input and output terminals being located a spaced distance from the extremities of the undulating conductive member to provide the characteristics set forth hereinabove while taking advantage of microconductor techniques to further reduce the size and allow dual-in-line delay line packages. Both of the above embodiments may be modified accordingly to provide a tapped delay line having the desirable characteristics set forth herein.

United States Patent 1 Lorber et al.

[ 1 PRECISION DISTRIBUTED PARAMETER DELAY LINE [761 Inventors: Harold Lorber, 3225 Burn Brae Dr.,

Dresher, Pa. 19027; Irving'Dubotf, 1513 Woodland Rd., West Chester,

[22] Filed: May 12, 1972 [21] Appl. No.: 252,617

[52] U.S. Cl. 333/31 R, 333/20, 333/70 T, 333/84 M, 328/56 [51] Int. Cl. H03h 7/30, l-10lp 3/08 [58] Field of Search 333/31 R, 70 T, 31 C, 333/84 R, 84 M; 328/56, 67, 66,121,151

[56] References Cited UNITED STATES PATENTS 2,832,935 4/1958 Tank 333/29 2,912,625 11/1959 Benson. 174/59 X 3,409,846 11/1968 Bray 333/20 3,418,604 12/1968 Ross 333/20 3,480,887 11/1969 Uhlir, Jr... 174/52 R X 3,585,534 6/1971 Senf 333/84 M X 3,629,738 12/1971 Senf 333/84 M X 3,629,740 12/1971 Merrill 333/84 M X 3,643,182 2/1972 Swanson 333/29 Primary ExaminerRudolph V. Rolinec Assistant Examiner-Marvin Nussbaum Attorney-Ostrolenk, Faber, Gerb & Soffen ABSTRACT A precision distributed parameter delay line for use in high speed circuitry requiring very precise nanosecond 1 Oct. 23, 1973 delay intervals. The delay line, in one preferred embodiment, comprises a section of coaxial cable transmission line having a central conductor and a coaxially aligned conductive sheath with the sheath preferably being insulated over its length. The section of co- 4 axial cable tranmission line functions as a low impedance delay'element of extremely small outer diameter whose length may be adjusted to provide delays of from tenths to hundreds of nanoseconds. The nature and size of the delay line is such as to make it extremely adaptable to being coiled so as to significantly reduce the amount of space which it occupies. A very short section of coaxial cable transmission line of similar design and impedance characteristics is coupled to the input and/or output ends of the coaxial cable transmission line section central conductor to improve the rise time and provide an extremely high delay' to rise time ratio, low insertion loss, low characteristic impedance and is adaptable for use over a wide frequency bandwidth.

The delay line may also take the form of a printed circuit of the microstrip type transmission line comprised of an elongated, preferably-undulating conductive strip separated from a conductive ground plane. by a suitable dielectric with input and output terminalsbeing located a spaced distance from the extremities of the undulating conductive member to provide the characteristics set forth hereinabove while taking advantage of microconductor techniques to further reduce the size andallow dual-in-line delay line packages. Both of the aboveembodiments may be modified accordingly to provide a tapped delay line having the desirable characteristics set'forth herein.

16 Claims, 7 Drawing Figures PRECISION DISTRIBUTED PARAMETER DELA LINE The present invention relates to delay lines and more particularly to a precision delay line structure utilizing an additional delay line section or sections to significantly improve rise time, reduce insertion losses and provide a delay line having a low impedance characteristic while at the same time providing precise delays in the nanosecond range.

BACKGROUND OF THE INVENTION.

Delay lines are presently employed in a wide variety of applications. Some very important applications exist in the computer area wherein it is required to provide for simultaneous presence of a plurality of signals at the input to a gate, for example, whereby some of these signals may pass through logic chains of differing lengths, thereby requiring delay lines to equalize the delays of such signals to insure their presence when they are required. Other areas such as radar communications and sophisticated electronics applications also have need for delay lines which provide precise delay intervals in the nano second range.

Some of the major problems existing in connection with conventional delay line structures are the poor rise and fall times, the high impedance characteristics of the delay lines, the narrow bandwidths 'in which conventional delay lines may be employed and the high insertion losses which occur in conventional delay lines. One of the most significant problems in conventional delay lines resides in their'poor delay to rise time ratio. One technique which has beenemployed in the prior art is the utilization of a'se'ries connected capacitor and resistor element connected between the central conductor of a coaxial cable transmission line and ground which is provided to improve the rise time characteristic of the delay line. However, this technique has led to a reduction in signal strength (i.e., increase in attenuation of the delayed output pulse) and ma change in the characteristic impedance of the delay line.

BRIEF DESCRIPTION OF THE INVENTION The present invention is characterized by providing a" distributed parameter delay line structure "of small size so as to occupy a relatively small amount of space as compared with conventional delay lines and which is provided with a short delay line section coupled across the input and/or output terminals of the delay line which short section acts to significantly improve the delay to rise time ratio and which further reduces the insertion loss and does not affect the low impedance characteristic of the delay line while at the same time being adaptable for use over a wide bandwidth.

In one preferred embodiment of the present invention, the delay line is comprised of a first coaxial cable transmission line section of extremely small outer diameter and having a length selected to provide the appropriate nanosecond delay. A second section of coaxial cable transmission line of similar physical design and characteristics has its central conductor connected to the input terminal of the delay line. Theconductive sheaths of both the second coaxial cable transmission line section and the delay line section are preferably grounded while the free end of the short second delay line section remains electrically isolated from the remainder of the circuit and functioning as a tuning element. It has been found that the resulting delay line structure provides an extremely fast rise time and hence a highdelay to rise time ratiowhile at the same time providing low insertion loss, low input impedance and is adaptable for use over a wide bandwidth.

The amount of delay is obtained by selecting a coaxial cable transmissionline delay line section of appropriate length and the delay line apparatus provides a very precise delay in the range from tenths to hundreds of nanoseconds with a precision of the order of i onehalf nanosecond.

A similar short coaxial type delay line section may be coupled across the output terminal of the delay line apparatus in a manner similar to that described hereinabove in connection with the short delay line section coupled across the input of the delay line to provide impedance matching between the output of the delayline and the input of an electrical circuit or other component connected thereto as well as improving rise time of the delayed signal.

Another preferred embodiment of the present invention employs microconductor techniques in which a conductive strip or coating preferably arranged in an undulating pattern is mounted upon an insulating substrate having a predetermined dielectric constant and being adapted to receive a ground plane upon its opposite surface so as toform a microstrip type delay line. The inputand output connections of the delay line are .spaced inwardly by predetermined distances from the extremities of the undulated conductive strip so as to provide effective short delay line sections functioning 1 delay line apparatus manufactured in accordance with the above techniques provides an extremely small and compact delay line structure which lends itself advantageously for use in a dual in line package. Delays of the order of tenths of hundreds of nanoseconds with the tolerance ofthe order of i: one-half nanosecond are obtained by etching or machining away the portion of the undulating conductive strip, with the amount etched or machined away being dependent upon'the particular delay interval desired. The characteristic impedance of the delay line may be controlled over a wide range through appropriate selection of a dielectric material and further by controlling its thickness.

Both types of delay lines as described hereinabove may be appropriately modified to provide a tapped delay line structure.

OBJECTS OF THE INVENTION It is therefore one primary object of the present invention to provide a novel delay line structure of extremely small size for providing delays of precise values within the nanosecond range.

Another object of the present invention is to provide a novel delay line apparatus of extremely small size for providing a precise delay interval within the nano second range and which incorporates an additional section or additional sections coupled to the input and output ends thereof for significantly improving the delay to rise time ratio without adversely affecting the characteristic impedance and other advantageous characteristics of the delay line structure.

Another object of the present invention is to provide delay lines having the characteristics as defined by the above objects in which the delay line structures is formed of coaxial cable transmission line sections of extremely small diameters.

Still another object of the present invention is to provide a novel tapped delay line structure having the characteristics as set forth in the objects recited hereinabove in which microconductor techniques are employed in the manufacture of the delay line structure.

Still another object of the present invention is to provide a novel tapped delay line structure having the characteristics as set forth in the objects recited hereinabove.

BRIEF DESCRIPTION OF THE FIGURES The above as well as other objects of the present invention will become apparent when reading the accompanying description in conjunction with the drawings in which:

FIG. 1 is a waveform useful in describing the various embodiments of the present invention and its advantages over the prior art.

FIG. 2 is a perspective showing one preferred type of coaxial cable transmission line which may be advantageously employed in the apparatus of the present invention.

FIG. 3 is a schematic diagram showing one preferred. embodiment ofa delay line structure designed in accordance with the principles of the present invention.

FIGS. 4a and 4b are perspective views showing other preferred embodiments of the present invention.

FIG. 5 shows another embodiment of the present invention in which delay lines of the type shown in FIGS. 4a and 4b may be stacked to provide a delay linestructure of a multiplicity of precise delay intervals and increase the delay time preferably within the nanosecond range.

FIG. 6 is a sectional view showing one delay line package which may be employed for encapsulating delay line structures of the type shown in FIGS. 4a 5.

DETAILED DESCRIPTION OF THE FIGURES The waveform of FIG. 1 is useful in evaluating and clarifying an understanding of delay line structures and their attendant shortcomings.

As shown in FIG. 1, the input pulse, which isa substantially square pulse of narrow pulse width t is typically measured at the 50 percent amplitude points.

The delay time T between the application of the input pulse at the input terminal of a delay line structure and the current of the output pulse at the output of the delay line structure is typically measured from the 50 percent amplitude point of the leading edge of the input pulse to the 50 percent amplitude point of the leading edge of the output pulse.

The input pulse rise time a, is the time duration measured between the instant in which the leading edge of the input pulse reaches 10 percent of its maximum amplitude and the instant at which it reaches 90 percent of its maximum amplitude. The output pulse rise time n is determined in a similar fashion. The dashed line portions of the waveform shown in FIG. 1 show common variations which typically occur in the output wave shape. The dotted line section b represents overshoot which is a continuation of theleading edge of the pulse typically caused by resonances within the delay This ratio is one measure of the quality of the delay line. The bandwidth characteristic of a delay line is determined by those frequencies which are capable of being passed by the delay line at a useful bandwidth (i.e., signals attenuated 3 db or less, for example). This is related to rise time approximately by bandwidth X rise time 0.4

The temperature ofa delay line is typically expressed as a-p'ercentage change in delay per change in degree C devices.'A delay line will shift" the phase of a sine wave an amount in degrees equal to 360 times the delay time X the frequency ,of the sine wave or The significant characteristic ofa delay line resides in its ability to provide an output pulse which appears at the output of a delay line a predetermined time interval after application of the input pulse at the input terminal of the delay line with the output pulse being as nearly exact in shape and pulse width to the input pulse as is practically possible. Conventional delay lines have been found to generate output pulses whose rise time, as defined hereinabove, and fall time (defined as the time interval between the instant at which the output pulse drops to percent of its maximum amplitude, excluding overshoot) to the time instant at which it falls to 10 percent of its maximum amplitude, also excluding overshoot, with the, rise and fall times of the output pulse being significantly increased as compared to the rise and fall times of the input pulse. Efforts to overcome such deficiencies have been undertaken in the prior art. One typical approach is to provide a series connected resistor and capacitor connected between the central conductor of a coaxial cable transmission line type delay line and ground potential in order to improve the rise and fall times of the output pulse. This technique, however, has led to a significant deviation in the characteristic impedance of the delay line which is defined as the impedance presented to an input pulse applied to the delay line.

The shortcomings of prior art delay line structures have led to the development of the present invention which overcomes the deficiencies of the prior art, including but not limited to the above mentioned deficiencies, as will be described more fully in connection with FIGS. 2-6 of this application.

Before entering into a description of the one preferred embodiment of the present invention, a description will first be given of a delay line structure of the Delay lines may also be employed as phase shifting (i.e., the surface remote from the conductor '11) has a conductive coating deposited or otherwise formed thereon so as to form a conductive sheath substantially coaxially aligned with and surrounding the central conductor 11. The resulting structure is then encapsulated within an elongated insulating sleeve 13 extending over substantially the entire length of the coaxial cable structure. An elongated conductive member 14 is run parallel .to the central conductor 11 and is'in intimate contact with the shield 12. This conductive member isknown as a drain wire and greatly facilitates electrical connection of the coaxial cable into an electrical or electronic circuit. The short. sections of conductive wire 14,14 are usually of a greater diameter than central conductor 11 and are typically of the order of 8 mils. The overall diameter of coaxial cable 10 is typically of the order of 25 mils.

Coaxial cable transmission line of the type shown in FIG. 1, due to its small size and design, is capable of providing an input impedance of the order of 50 ohms.

This size is substantially smaller than conventional coaxial cable transmission lines.

The coaxial cable transmission line 10 of FIG. 2 may be used to. advantage in the preferred embodiment 20 as shown in FIG. 3 of the present application, which is comprised of a coaxial cable transmission line section 10" which may be of the design shown in FIG. 2 and whichis provided with input and output terminals e and e respectively. The delay time of coaxial cable transmission line 10' is controlled by its length. For example, in cases where a delay line of 15 nanoseconds is desired, coaxial cable transmission line 10' may have a length ofthc o'rder of 10 feet. The delay to rise time ratio-of the delay line structure of FIG. 3 is significantly improved through the employment of a second delay line section 10" substantially identical in design and operating characteristics to the cable section 10'. The section 10" is substantially shorter in length than the section 10', as will be described in greater detail hereinbelow and has its central conductor 11" electrically connected to a central conductor 11 of coaxial cable section 10' by means of a separate conductor 15. The separate conductor may obviously be omitted and the extremities of conductors 11' and 11" may be directly electrically connected such as, for example, either mechanical connection or a soldered connection. The short conductive strips 14' and 14" of coaxial cable transmission line sections 10' and 10', respectively, are electrically connected to one another and are preferably grounded.

As was described hereinabove, the length of section 10' is determinative of the desired delay time. The length of section 10" is selected as to provide the optimum delay torise time ratio and in applications for providing delay times of the nanosecond range is typically of a length in the range from 5 to 20 percent of the length in the range from 10'.

In applications where delay times of the order of hundreds of nanoseconds are required, it is preferred that the coaxial cable transmission line sections 10' may be tightly (or loosely) wound in a loop so as to reduce its overall'size (i.e., the space which it occupies). Likewise, the shorter section 10" may be wound within the same loop. It should be noted that the free endof section 10" is not connected in electrical circuit and remains floating. Nanosecond delay lines of the type shown in FIG. 3 have been found to provide delay to rise time ratios which are significantly improved as compared with conventional devices and techniques.

FIGS. 4a and 4b show'additional preferred embodiments of the present invention which incorporate microconductor techniques. FIG. 4a shows a delay line structure 20 embodying the concepts described hereinabove and comprised of a sheet of dielectric material 21 having high dielectric strength and specific dielectric constant and preferably taken from the group of materials described hereinabove in connection with the embodiment of FIG. 3 and the coaxial cable transmission line structure of FIG- 2. The undulating conductive coating 22 is deposited upon one surface 21a of dielectric sheet 21. A conductive ground plane 23 is coated on the opposite surface 2lb of dielectric sheet 21 so as to. form a microstrip transmission linecircuit element. The conductive strip 22 which is arranged in an undulating pattern cooperates with conductive ground plate 23 to form a delay line whose physical length may be adjusted to provide the appropriate nanosecond delay. The selection of the appropriate material for dielectric sheet 21 and its thickness determines the characteristic impedance of the delay line. Electrical coupling to the delay-line is provided by a short conductive lead 24 which is electrically connected at a point 25 spaced inwardlyfrom one extremity of conductive strip 22. Electrical connection may preferably be made by soldering short lead 24 to strip 22 at point 25.

Electrical connection from the output of the delay line device to the input of an associate circuit (not shown for purposes of simplicity) may be provided for through the use of a second short lead 26 which is electrically connected at a point 27 spaced inwardly from the opposite extremity of undulating conductive strip 22.

The physical distance between points 25 and 27 measured along the undulating conductive strip 22 determines the amount of delay which the delay line apparatus provides. Thus by :moving points 25 and 27 either closer together or further apart, the delay time of the circuit is accordingly respectively decreased or increased.

The length L of the undulating conductive surface measured between its extremity 22a and point 25 functions in the same manner as the short delay line section 10" shown in FIG. 3 so as to significantly improve the rise time of the output pulse. Similarly, the length L of the undulating conductive strip 22 measured between its extremity 22b and point 27 likewise functions to improve the rise and fall time of the output pulse as well as controlling its shape so as to be as nearly identical to the input pulse as is practically possible and further functions to provide good impedance matching between the output of the delay line device 20 and the input of an electrical circuit connected thereto.

Points 25 and 27 are located in accordance with the length of the desired delay time. The length L, (and/or L of the short delay line section is then controlled by etching, machining away or otherwise removing that amount of conductive strip from the extremity as is required to optimize the rise and fall times of the output pulse. For example, let it be assumed that a desired delay dictates that the input and output leads be connected at points 25 and 27. After so locating these points, the length of the short section of delay line coupled to the input terminal is then optimized. Let it be assumed that this length should be L In this case a portion P of the forward extremity of undulating conductive strip 27 would be removed. Obviously, a similar operation would be performed in optimizing the length L of the short delay line section provided at the output (if such a section is either needed or desirable).

FIG. 4b shows an alternative embodiment to that of FIG. 4a wherein like elements are designated with like numerals. The major difference between the embodiments of FIGS. 4a and 4b reside in the fact that a different conductive pattern is provided on the upper surface 21a of dielectric sheet 21. As shown in FIG. 4b, the single undulating conductive strip 22 is replaced by three separate strips 28, 29 and 30 deposited or otherwise formed upon surface 21a. This arrangement enables a delay line to be made without a ground plane member. However, it should be noted that FIG. 4a may be modified so as to divide the single undulating conductive strip into a plurality of shorter conductive strips of either similar or dissimilar length by machining away portions thereof such as, for example, at 22c and 22d so as to form three separate delay line sections which may be used either independently or joined as desired.

Returning to the embodiment of FIG. 4b, the conductive strips 28, 29 and 30 are arranged in a substantially spiralling fashion so as to provide conductive strips of substantially great length within a reduced surface area and/or volume as compared with arranging the conductive strips in straight line fashion and in a spaced parallel arrangement. Whereas the embodiment of FIG. 4a shows an undulating' pattern andthe embodiment of FIG. 4b shows a substantially spiralling pattern, it should be understood that any other pattern may be employed which is conducive to providing a conductive strip of desired length while providing a package of minimul surface area and/or volume.

Conductive strips 28 and 30 act as the ground return for strip 29. Dielectric sheet 21 is used as a support structure. The input and output terminals of the individual strips are located therealong depending upon the particular delay time desired. For example, strips 28 and 30 may be provied with input points at 31 located a spaced distance inwardly from their inner extremities 28a and 30a and electrically connected to a short lead section 32 such as, for example, by soldering. Likewise, output points may, for example, be located at points 33 and electrically connected to a short conductor 34 which is likewise soldered or otherwise connected at point 33. The remaining portions of lengths L and L function in the same manner as those sections L (or L,') and L of FIG. 4a or the short section of FIG. 3 in the same manner as was described hereinabove. If desired, strips 28-30 may spiral along continuous curves.

FIG. 5 shows another preferred embodiment of the present invention wherein delay line devices 20, 20a and 20b of the type shown in FIG. 4a may be stacked so as to provide resultant time delay equal to the sum of the time delays provided by each individual delay line device. For example, a short conductor 24 may be electrically connected to conductor strip 22 at point 25 wherein point 25 may be selected as the input terminal of the delay line structure. The output end 27 of delay line structure 20 is then electrically connected to point 27' of strip 22' provided in delay line structure 20a by means of a short conductive section 26. This pattern may be repeated whereby the opposite extremity of undulating conductive strip 22 is electrically connected to one extremity (not shown) of delay line device 20b with the ultimate output connection being provided by connecting a conductive strip 26 to output point 27" on delay line device 20b. Obviously, any number of delay line sections may be stacked in this manner to provide the necessary delay time.

FIG. 6 shows one manner in which delay line devices of the type shown, for example, in FIGS. 4a and 4b may be encapsulated and packaged as a dual in-line device. The prepackaging assembly 40 of FIG. 6 is comprised of a base member 41 having a plurality of input leads 42 and output leads 43 arranged along longitudinal sides of base member 41. The leads 42 and 43 are imbedded within base member 41 and have a short section thereof protruding upwardly through base member 41 for electrical connection to delay line devices such as thedelay line devices 20 and 20 of FIG. 6. The leads 42 and 43 also protrude downwardly from base member 41 for the purpose of providing electrical connections to peripheral circuitry (not shown for purposes of simplicity).

The bottom surfaces of the delay line devices are preferably secured to thetop surface of base member 41 by means ofa pressure sensitive adhesive or suitable contact cement. Electrical connections are provided between the leads 42 and 43 and their associated delay line devices. For example, delay line device 20 is shown as being electrically connected to selected ones of the leads 42 and 43 by means of short conductors 44 and 45, respectively. Similar electrical leads 46 and 47 are shown as being provided for electrical connection between selected ones of leads 42 and 43 and the delay line device 20.

The package assembly 40 is further comprised of a hollow lid member 40 designed to be positioned upon the base member 41 in the manner shown. The mating edges of members 48 and 41 may be sealed to one another by a suitable contact cement. Alternatively, the mating edges may be joined by the application of a suitable solvent which causes fusion and joining therebetween.

Preferably, the individual delay line devices are encapsulated within a material which may be provided thereon by a dipping operation, for example. Preferably, this operation should be preceded by providing an electrical connection in the form of leads 44 and 45, for example. As an alternative arrangement, the encapsulated delay line devices may also be joined to the top surface of base member 41 by application of an adhesive to their mating surfaces so as to fuse and join the delay line devices to the base member 41.

The hollow interior region defined by the base member 41 and cover member 48 is preferably filled with a foamed plastic material which functions to cushion and protect the delay line devices mounted therein while at the same time assisting and maintaining the appropriate dielectric environment for the delay line devices. The foamed plastic material which may, for example, be a foamed polyolefin or polyurethane may be inserted after mounting of the cover member 48 by providing a slot 48a in the top surface of the cover member through which the foamed material may be introduced. After filling the entire interior space, any excess foam may be wiped off. The slot 48a provided in the upper surface of cover member 48 may be covered by a cover strip or sheet 49 which may, for example, be formed of a paper material having a pressure-sensitive surface so as to cover over slot 48a while at the same time providing indicia identifying the particular product and its delay values to facilitate identification and use thereof. The cover member 48 may be provided with a bevelled corner 48b which serves as a means for identifying which row of leads 42 and 43 represents the input and respectively the output leads of the delay line devices. In a similar fashion, a corner of the base member may be bevelled along the edge associated with the bevel 48b provided in cover member48 so as to provide a neat compact package. The introduction of the foamed plastic material provides sufficient cushioning for the delay line devices housed therein so as to eliminate the need for separate mounting of the delay line devices if desired.

To prevent oxidation and/or corrosion of the ground plane and conductive strips they may be coated with line sections 10a and lb', with an output lead a e and e being provided at the common terminal between each end to end connector. The delayat any such output is the sum of the delays of each section provided between e and the output terminal selected. A short coaxial section may be provided only at the first section 10' as shown in FIG. 3 or a section similar to 10" may be provided at each common connection between adjacent sections.

The embodiments of FIGS. 4-6 may be modified in a similar fashion to provide a tapped delay line structure.

It can be seen from the foregoing description that the present invention provides a novel delay line device which is extremely small in size, has an extremely low input impedance and provides delayed output signals having significantly improved rise and fall times as compared with conventional structures while at the same time providing precise delay time intervals in the nanosecond range with tolerances of the order of one-half nanosecond.

Although there has been described a preferred embodiment of this novel invention, many varitions and modifications will now be apparent to those skilled in the art. Therefore, this invention is to be limited, not by the specific disclosure herein, but only by the appending claims.

The embodiments of the invention in which an exclusive privilege or property is claimed are defined as follows: v

l. A delay line device comprising input means for receiving an input pulse to be delayed;

coaxial cabletransmission line means'having a predetermined length;

said input means being coupled to said coaxial cable transmission line means a'spaceddistance from a first extremity of said coaxial cable transmission line means;

outputmeans coupled to the opposite end of said coaxial cable transmission line means for coupling the delayed input signal to an external circuit;

the length of the delay interval being determined by the electrical length of said coaxial cable transmission line means measured between said point of connection with said input means and the opposite end of said coaxial cable transmission line means; .said first extremity being electrically isolated from the remainder of said delay line as well as any associated circuitry;

the portion of said coaxial cable transmission line meansbetween said first extremity and said point of connection having an electrical length substantially shorter than the remainder of said coaxial cable transmission line means and'being adapted to improve the rise time of the delayed input pulse appearing at said output means.

2. A delay line device comprising output means for receiving an output pulse to be delayed;

coaxial cable transmission line means having a predetermined length;

said'output means being coupled to one end of said coaxial cable transmission line means;

said output means being coupled to said coaxial cable transmission line means a spaced distance inward from the opposite end thereof for coupling the delayed input signal to an external circuit;

the length of the delay interval being determined by the electrical length of said coaxial cable transmission line means measured between the point of connection with said output means and said one end of said coaxial cable transmission line means;

said opposite end being electrically isolated from the remainder of said delay line as well as any associated circuitry;

the portion of said coaxial cable transmission line means between said one end and said point of connection having an electrical length substantially shorter than the remainder of said coaxial cable transmission line means and being adapted to improve the rise time of the delayed input pulse appearing at said output means.

3. The delay line device of claim 1 wherein said coaxial cable transmission line means is comprised of a first coaxial cable transmission line including a central conductor;

dielectric means surrounding said central conductor and a conductive sheath surrounding said dielectric means and substantially coaxially aligned with said central conductor;

insulation means covering said conductive sheath.

4. The delay line device of claim 3 wherein the portion of said coaxial cable transmission line means between said first extremity and said point of connection is a second coaxial cable transmission line including a central conductor;

dielectrical means surrounding said central conductor, and a conductive sheath surrounding said dielectric means and substantially coaxially aligned with said central conductor; insulation means covering said conductive sheath; means electrically connecting adjacent ends of first and second coaxial cable transmission line central conductors; means for grounding adjacentends of the first and second coaxial cable conductive sheaths. 5. A delay line device comprising input means for receiving an input pulse to be delayed;

a transmission line means having a predetermined length; said input means being coupled to said transmission line means a spaced distance from a first extremity of said transmission line means;

output means coupled to the opposite end of said transmission line means for coupling the delayed input signal to an external circuit;

the length of the delay interval being determined by the electrical length of said transmission line means measured between said point of connection with said input means and the opposite end of said transmission line means;

said first extremity being electrically isolated from the remainder of said delay line as well as any associated circuitry;

the portion of said transmission line means between said first extremity and said point of connection having an electrical length substantially shorter than the remainder of said transmission line means and being adapted to improve the rise time of the delayed input pulse appearing at said output means;

said transmission line means comprising:

a layer of dielectric material;

an elongated conductive strip being provided on one surface of said layer;

a conductive ground plane being provided 'on the opposite surface of said layer;

said point of connection being a spaced distance in from one extremity of said conductive strip. 6. The delay line device of claim wherein said conductive strip is arranged in an undulating fashion on said layer.

7. The delay line of claim 5 wherein said delay line further comprises at least one additional conductive strip arranged on said one surface of said layer and being speced and electrically isolated from said first strip.

8. The delay line device of claim 5 wherein said conductive strips are arranged in an undulating fashion on said layer.

9. The delay line device of claim 5 further comprising a housing for said delay line device;

said housing comprising a base member having input and output leads each having a first end protruding into the interior of said housing and a second end protruding from the exterior of said housing;

means for electrically coupling the first ends of said leads respectively to the input and output means of said delay line device;

a cover member sealed to said base member for encapsulating said delay line device;

the interior region of said housing being filled with a foamedinsulating material for rendering said delay line device shock proof and for maintaining the desired dielectric medium within said housing.

10. The delay line device of claim 9 wherein said foamed insulating material is taken from the group of materials comprising polyolefins and polyurethanes.

11. A delay line device comprising input means for receiving an input pulse to be delayed;

transmission line means having a predetermined length;

said input means being coupled to said transmission line means a spaced distance from a first extremity of said transmission line means;

output means coupled to the opposite end of said transmission line means for coupling the delayed input signal to an external circuit;

the length of the delay interval being determined by the electrical length of said transmission line means measured between said point of connection with said input means and the opposite end of said transmission line means;

said first extremity being electrically isolated from the remainder of said delay line as well as any associated circuitry; the portion of said transmission line means between said first extremity, and said point of connection having an electrical length substantially shorter than the remainder of said transmission line means and being adapted to improve the rise time of the delayed input pulse appearing at said input means;

said transmission line means being comprised of first,

second and third spaced conductive strips arranged in a spiral fashion on an insulating substrate;

the point of connection of the input means being a spaced distance inward from a first extremity of the second conductor.

12. A tapped delay line device for providing a plurality of selectable delays comprising;

a plurality of coaxial cable transmission line means;

input means for receiving an input pulse to be delayed; said input means being coupled to one end of a first one of said coaxial cable transmission line means;

a plurality of output means for electrically connecting the second end of said first coaxial cable transmission line means and the remaining ones of said coaxial cable'means in end to end fashion;

drain means comprising'a short coaxial cable transmission line means having a first end electrically connected to the common junction between said input means and said one end of said first coaxial cable transmission line means and having a second end unterminated for improving the rise time of the delayed input pulse appearing at any one of said output means, the length of said drain means being shorter than any one of said plurality of coaxial cable transmission line means.

13. The delayline device of claim 12 wherein said plurality of coaxial cable transmission means and said drain means are each comprised of a first coaxial cable transmission line including a central conductor; dielectric means surrounding said central conductor and a conductive sheath surrounding said dielectric means 13 14 I and substantially coaxially aligned with said central said point of connection being a spaced distance in conductor; insulating means covering said conductive from the extremities of said conductive Strips sheath; said output means each being coupled between whereby the portion of said strip between said adjacent ends of the central conductors of associated point of connection and the extremity thereof funccoaxial cables. tions to enhance the rise time of the delayed signal.

14. The delay line device of claim 1 wherein said 00- 15. The delay line device of claim 14 wherein one of axial cable transmission means comprises: said strips is a ground return.

a layer of dielectric material; 16. The delay line device of claim 14 comprising a plurality of elongated conductive strips being prothree strips; the outer two strips serving as a ground revided on one surface of said layer at spaced interturn.

vals; 

1. A delay line device comprising input means for receiving an input pulse to be delayed; coaxial cable transmission line means having a predetermined length; said input means being coupled to said coaxial cable transmission line means a spaced distance from a first extremity of said coaxial cable transmission line means; output means coupled to the opposite end of said coaxial cable transmission line means for coupling the delayed input signal to an external circuit; the length of the delay interval being determined by the electrical length of said coaxial cable transmission line means measured between said point of connection with said input means and the opposite end of said coaxial cable transmission line means; said first extremity being electrically isolated from the remainder of said delay line as well as any associated circuitry; the portion of said coaxial cable transmission line means between said first extremity and said point of connection having an electrical length substantially shorter than the remainder of said coaxial cable transmission line means and being adapted to improve the rise time of the delayed input pulse appearing at said output means.
 2. A delay line device comprising output means for receiving an output pulse to be delayed; coaxial cable transmission line means having a predetermined length; said output means being coupled to one end of said coaxial cable transmission line means; said output means being coupled to said coaxial cable transmission line means a spaced distance inward from the opposite end thereof for coupling the delayed input signal to an external circuit; the length of the delay interval being determined by the electrical length of said coaxial cable transmission line means measured between the point of connection with said output means and said one end of said coaxial cable transmission line means; said opposite end being electrically isolated from the remaindeR of said delay line as well as any associated circuitry; the portion of said coaxial cable transmission line means between said one end and said point of connection having an electrical length substantially shorter than the remainder of said coaxial cable transmission line means and being adapted to improve the rise time of the delayed input pulse appearing at said output means.
 3. The delay line device of claim 1 wherein said coaxial cable transmission line means is comprised of a first coaxial cable transmission line including a central conductor; dielectric means surrounding said central conductor and a conductive sheath surrounding said dielectric means and substantially coaxially aligned with said central conductor; insulation means covering said conductive sheath.
 4. The delay line device of claim 3 wherein the portion of said coaxial cable transmission line means between said first extremity and said point of connection is a second coaxial cable transmission line including a central conductor; dielectrical means surrounding said central conductor, and a conductive sheath surrounding said dielectric means and substantially coaxially aligned with said central conductor; insulation means covering said conductive sheath; means electrically connecting adjacent ends of first and second coaxial cable transmission line central conductors; means for grounding adjacent ends of the first and second coaxial cable conductive sheaths.
 5. A delay line device comprising input means for receiving an input pulse to be delayed; a transmission line means having a predetermined length; said input means being coupled to said transmission line means a spaced distance from a first extremity of said transmission line means; output means coupled to the opposite end of said transmission line means for coupling the delayed input signal to an external circuit; the length of the delay interval being determined by the electrical length of said transmission line means measured between said point of connection with said input means and the opposite end of said transmission line means; said first extremity being electrically isolated from the remainder of said delay line as well as any associated circuitry; the portion of said transmission line means between said first extremity and said point of connection having an electrical length substantially shorter than the remainder of said transmission line means and being adapted to improve the rise time of the delayed input pulse appearing at said output means; said transmission line means comprising: a layer of dielectric material; an elongated conductive strip being provided on one surface of said layer; a conductive ground plane being provided on the opposite surface of said layer; said point of connection being a spaced distance in from one extremity of said conductive strip.
 6. The delay line device of claim 5 wherein said conductive strip is arranged in an undulating fashion on said layer.
 7. The delay line of claim 5 wherein said delay line further comprises at least one additional conductive strip arranged on said one surface of said layer and being speced and electrically isolated from said first strip.
 8. The delay line device of claim 5 wherein said conductive strips are arranged in an undulating fashion on said layer.
 9. The delay line device of claim 5 further comprising a housing for said delay line device; said housing comprising a base member having input and output leads each having a first end protruding into the interior of said housing and a second end protruding from the exterior of said housing; means for electrically coupling the first ends of said leads respectively to the input and output means of said delay line device; a cover member sealed to said base member for encapsulating said delay line device; the interior region of said housing being filled with a foamed insulating material for rendering said delay line device shock proof and for maintaining the desired dielectric medium within said housing.
 10. The delay line device of claim 9 wherein said foamed insulating material is taken from the group of materials comprising polyolefins and polyurethanes.
 11. A delay line device comprising input means for receiving an input pulse to be delayed; transmission line means having a predetermined length; said input means being coupled to said transmission line means a spaced distance from a first extremity of said transmission line means; output means coupled to the opposite end of said transmission line means for coupling the delayed input signal to an external circuit; the length of the delay interval being determined by the electrical length of said transmission line means measured between said point of connection with said input means and the opposite end of said transmission line means; said first extremity being electrically isolated from the remainder of said delay line as well as any associated circuitry; the portion of said transmission line means between said first extremity and said point of connection having an electrical length substantially shorter than the remainder of said transmission line means and being adapted to improve the rise time of the delayed input pulse appearing at said input means; said transmission line means being comprised of first, second and third spaced conductive strips arranged in a spiral fashion on an insulating substrate; the point of connection of the input means being a spaced distance inward from a first extremity of the second conductor.
 12. A tapped delay line device for providing a plurality of selectable delays comprising: a plurality of coaxial cable transmission line means; input means for receiving an input pulse to be delayed; said input means being coupled to one end of a first one of said coaxial cable transmission line means; a plurality of output means for electrically connecting the second end of said first coaxial cable transmission line means and the remaining ones of said coaxial cable means in end to end fashion; drain means comprising a short coaxial cable transmission line means having a first end electrically connected to the common junction between said input means and said one end of said first coaxial cable transmission line means and having a second end unterminated for improving the rise time of the delayed input pulse appearing at any one of said output means, the length of said drain means being shorter than any one of said plurality of coaxial cable transmission line means.
 13. The delay line device of claim 12 wherein said plurality of coaxial cable transmission means and said drain means are each comprised of a first coaxial cable transmission line including a central conductor; dielectric means surrounding said central conductor and a conductive sheath surrounding said dielectric means and substantially coaxially aligned with said central conductor; insulating means covering said conductive sheath; said output means each being coupled between adjacent ends of the central conductors of associated coaxial cables.
 14. The delay line device of claim 1 wherein said coaxial cable transmission means comprises: a layer of dielectric material; a plurality of elongated conductive strips being provided on one surface of said layer at spaced intervals; said point of connection being a spaced distance in from the extremities of said conductive strips whereby the portion of said strip between said point of connection and the extremity thereof functions to enhance the rise time of the delayed signal.
 15. The delay line device of claim 14 wherein one of said strips is a ground return.
 16. The delay line device of claim 14 comprising three strips; the outer two strips serving as a ground return. 